Is there a single word for something that is simultaneously not interesting and not boring?

I am looking for a word that would describe a concept or activity, such as playing a game X, that is¹ neither boring nor interesting. In other words, it should mean ‘neutral’ wrt intrestingness (~ boringness) but still comparable on the scale of intrestingness to both ‘boring’ and ‘interesting’.

An example sentence would be

As far as I'm concerned, long-distance running is [insert word]; it is not boring but it's also not interesting.

Criteria²

1. Has to be unambiguous³, and may consist of two words at most.


2. Has to be a single word.


3. Should be formal in the sense that it is included in Cambridge Dictionary, or Merriam Webster, or both.


4. Should not contain negating prefixes, such as ‘un-’.

Does such a word exist in the English language?

For readers' convenience, please state which criteria you believe your word suggestion has met. You may do so, e.g., by adding a disclaimer at the top or bottom of your answer. Simply writing (1., 2.) is sufficient.

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¹ Assume a ternary system of intrestingness.

² If not all criteria can be met, you may relax the requirements from bottom to top, in the following order: 4. -> 3. -> 2. -> 1. Answers with the smallest number of relaxed criteria in this order will be preferred in accepting. For example, fulfilling (1., 2., 3.) is better than achieving (1., 3., 4.). Situations where a higher priority ordering fulfills fewer criteria than a lower priority vector, such as (1.) vs (3., 4.), will be assessed on a case-by-case basis.

³ Words such as ‘unappealing’ thus even fail criterium 1 because in a three-valued system ‘unappealing’ ~ ‘not appealing’ ~ ‘not interesting’ can be taken to mean either ‘boring’ or ‘neutral wrt intrestingness’.